標題:
Maths二元一次......
發問:
1)Island A and B are 114km apart. It takes 3 hours 48 minutes for a boat to travel downstream from island A to island B. However, it takes 6 hours for the boat to travel upstream form island B back to island A. What is the speed of the boat in still water? What is the speed of water flow?
Let the speed of the boat in still water be x km / h while that of the water flow be ykm / h. In the downstream journey, the speed of the boat is ( x + y ) km / h. 3h 48 min = 3.8h, so 114 / 3.8 = x + y x + y = 30 --- ( 1 ) In the upstream journey, the speed of the boat is ( x - y ) km / h. 114 / 6 = x - y x - y = 19 --- ( 2 ) ( 1 ) - ( 2 ) : x + y - x + y = 30 - 19 2y = 11 y = 5.5 x - 5.5 = 19 ( Sub y = 5.5 into ( 2 )) x = 24.5 Hence the speed of the boat in still water is 24.5km / h and the speed of the waterflow is 5.5km / h.
其他解答:
Maths二元一次......
發問:
1)Island A and B are 114km apart. It takes 3 hours 48 minutes for a boat to travel downstream from island A to island B. However, it takes 6 hours for the boat to travel upstream form island B back to island A. What is the speed of the boat in still water? What is the speed of water flow?
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最佳解答:Let the speed of the boat in still water be x km / h while that of the water flow be ykm / h. In the downstream journey, the speed of the boat is ( x + y ) km / h. 3h 48 min = 3.8h, so 114 / 3.8 = x + y x + y = 30 --- ( 1 ) In the upstream journey, the speed of the boat is ( x - y ) km / h. 114 / 6 = x - y x - y = 19 --- ( 2 ) ( 1 ) - ( 2 ) : x + y - x + y = 30 - 19 2y = 11 y = 5.5 x - 5.5 = 19 ( Sub y = 5.5 into ( 2 )) x = 24.5 Hence the speed of the boat in still water is 24.5km / h and the speed of the waterflow is 5.5km / h.
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